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Birds are both flying dinosaurs and flying reptiles. Yes, that's potentially confusing.
To understand the apparent contradiction, you have to understand how modern classification of organisms works (phylogenetic systematics). Under the old (Linnean) classification system, Reptilia (reptiles) was an order and Aves (birds) was a separate order. Phylogenetic ...

The joint you are thinking (I assume) of is not a knee, nor is it an elbow, instead it is an ankle which is bending the same way as us humans. You can see from the below diagram that the knee - the joint between the femur and tibia - is just further up the leg normally hidden by feathers.
Birds have a comparatively elongated metatarsus which gives the ...

Almost definitely (I'm not a regular birder) European Green Woodpecker (latin name: Picus viridis) and it is native to your area according to its species distribution map.
"Green woodpeckers are the largest and most colourful woodpeckers
native to Britain. They are easily recognised by their laughing
‘yaffle’ call, which they use to demarcate their ...

The question is all about semantics. One can call reptiles whatever (s)he wants. The question is what do we define as being a reptile? And the answer is that there are two possible definitions, a common "bad" definition (Definition 1) and a phylogenetic-based "good" definition (definition 2). I think your confusion comes from the use of the same term to mean ...

Birds have a body part known as the nicitating membrane otherwise known as the "third eyelid". This part has become vestigial in humans, where it remains as the plica semilunaris.
This image of a masked lapwing clearly shows its nicitating membrane in action, where it covers the eye in a horizontal motion. This is analogous to blinking in humans, and the ...

I just weighed a pigeon tail feather (~10 cm) long. The mass was 0.05 g. Although all tail feathers are not equal in length (and all pigeons are not equal in size), this is probably a good approximation.
Measuring the drag coefficient is going to be very challenging, because it will vary with the orientation of the oncoming airflow. A feather falling with ...

The male kakapo (Strigops habroptila) in that video is called Sirocco. Kakapo were (and still are) very close to extinction, so in the 1980s the Kakapo Recovery Programme was launched. As part of this programme, rangers monitor all known kakapo in the wild, visiting their nests and generally ensuring they are in good health. When Sirocco was a young chick, a ...

I looked up winglets so I had context for this answer. I'm interpreting winglets as the vertical tips at the end of airplane wings. If so, then you are correct. The spread primary feathers of soaring birds like eagles function as winglets (Tucker 1993). Airbus has a biomimicry web page devoted to some of the biological designs, including winglets, they ...

Various features of brain,skull and beak anatomy help to achieve protection.
A paper was published in PLoSOne in 2011 on this very topic:
Why do woodpeckers resist head impact injury: a biomechanical investigation
There is also a very readable summary on the BBC website. I advise that you read the whole article, but here is a quotation which lists the ...

The hoatzin has a digestive system that makes use of bacterial fermentation. Many other birds also consume grass, e.g. ostriches, ducks and geese.
There's also a large body of literature on how birds can digest cellulose.

Flying came first, as far as we know. The earliest known bird (currently), Archaeopteryx lithographica, already had aerodynamic feathers (Feduccia and Tordoff, 1979). The Solnhofen Limestone, where it was discovered, is ~145 million years old, so we can place the "when" flight evolved to greater than or equal to that time.
Gansus yumenensis is regarded as ...

This looks pretty much like a female zebra finch to me (the male have a more prominent feather pattern). See this picture:
These birds are not native in Europe, this is correct. But it is always possible that birds escape captivity (or are released) and the live in countries where they originally not belong. I think this is the case with the zebra finch ...

This is a Cattle Egret (Bubulcus ibis), which is a heron in its breeding plumage. When not breeding, the bird is white. See the images for comparision:
Breeding cattle egret with colored feathers.
Nonbreeding cattle egret, completely white.

This phenomenon is called tonic immobility. And those speculations you've mentioned are wrong: they do get back on their feet, only remain in that state for a prolonged time, which depends on the distance and eye contact with whoever laid the chicken on its back, as stated here.
From this experiment, it can be concluded, that this behavior in which the ...

In mammals there are only two species (known, there may well be others) where males lactate. They are both species of bats and this paper discusses the evolutionary mechanisms that could underlie male lactation. I have ignored human cases because they are more of an unusual occurrence (often brought on by severe dietary stress) rather than an evolved ...

The question is probably more complicated than it seems because, if I am not wrong, the word adaptation here is understood at the group level.
Definitions of adaptation
Unfortunately, there is not such thing as a single, standard definition of adaptation. But for most cases the accurate definition the author is using is not of much importance as all of the ...

The logical assertion "winglets have not happened in a long time, therefore they are not advantageous" is incorrect.
It is possible for an advantageous trait not to evolve even when advantageous, if there is no "path" to it. The trait only occurs gradually, in small incremental steps. If intermediary steps are harmful, the trait will not occur, even if the ...

LG stands for "linkage group". It seems the Chicken Genome Sequence group (Hillier et al., 2004) allocated several linkage groups (alleles or genes which tend to be inherited together) to the microchromosomes (tiny chromosomes typical of birds and reptiles), in this case called "linkage group E64" and "linkage group E22....". There are a load more ...

I'm not really inside the field but few weeks ago I noticed a Plos One article that was dealing with this. Indeed albatross can fly for thousands of miles and this is possible at no mechanical cost, because they use a dynamic way of flight that takes the energy from wind (dynamic soaring) (ref-1). Their muscle-skeletal system further evolved so that no ...

Most species of birds have 2 foveas, the temporal fovea and the central fovea.
temporal fovea, which is like ours in the sense that it looks straight
ahead and offers binocular vision (i.e. the temporal foveas of both
eyes point in the same direction). But birds also have a central
fovea, which points sideways and is, obviously, monocular (i.e., ...

There are two possibilites with evolutionary processes: The development either never went into this direction or it brought no advantages. Besides this two possibilities the claims from the other forum are wrong. Birds (not all of them though) do have winglet-like structures. If you look at big birds, you can see feathers on the end of the wings looking like ...

It's the same stuff that makes up most sea shells, calcium carbonate, $CaCO_3$.
Incidentally, this explains why egg shells dissolve in vinegar (acetic acid which, since it is an acid, provides the Hydrogen ions in the reaction below):
$CaCO_3+ 2H^+ -> Ca^{2+} + H_2O +CO_2$
This simple reaction (which is what would happen in your stomach as well) ...

All animals develop in this way, whether they are oviparous (developing in an egg) or viviparous (developing inside their mother, or live-birth).
From Wild Birds Unlimited:
All mammals have navels or belly buttons where the umbilical cord distributes nutrients between a mother and her fetus. After birth, the umbilical cord is cut and a scar develops ...

It's a Black Crowned Night Heron, Nycticorax nycticorax, in my opinion - you can read more about it here. Key to it's identification is the shape of the body and bill, it's characteristic of species from the heron family such as the green heron. The range is right and the red eye is a good clue too.

This is a story I have been told as well when I was a kid. Usually this is related to the foreign smell that the humans leave on the chick. However, this seems to be an urban legend, as birds have not a great sense of smell.
Snopes says about this:
However, Mother birds will not reject their babies because they smell
human scent on them, nor will ...

A trait is said to be adaptive when it causes fitness to increase. Fitness is generally understood as the (relative) contribution to future generations in terms of offspring or genes. The trait is selected for by the environment and hence increases fitness.
In the paper of Dey et al. this is the fitness of the parent birds. Hatching asynchrony causes size ...

Obviously, as you point out, some birds, such as waterbirds (ducks, puffins, auks, sandpipers) are perfectly fine in the rain, as they spend much of their time in the water anyhow and have oil glands that waterproof their feathers.
For other birds, rain can increase heat loss. For instance, rain increases metabolism by up to 22% in eagles (Stalmaster & ...

I don't know of studies specifically of boat-tailed grackle flight, so I'll focus on elongated tails in general and come back to grackles at the end.
Long tails in birds are obviously interesting from the standpoint of sexual selection. Going all the way back to Darwin, one hypothesis has been that females prefer males with long tails. There seems to be ...